I don't know the tested top speed for the CB650, but most other vertical twin 650s, Triumph, Yamaha, etc. , would get very close to or exceed 100 mph. The Honda could be a little down on power compared to it's contemporary competitors or more likely, it could use a little tuning - ignition timing, air filter, clean carbs...
Unless you are planning on racing your CB650 I would not worry how fast is goes, as long as it can go the speed limit. You should never need to reach the CB650s top speed of 118mph to 125mph under normal riding conditions. Those are unsafe speeds for people who are not professionals.
Well depending on the year and the exact kind of your CB650 and if the tachometer is redlined when you are hitting 90mph then yes that is as fast as it will go. Generally, there average is about 110, but there were a few years that 90mph was the maximum.
Yes this is perfectly normal, the aerodynamics of the bike itself limit the speed by creating drag, check the tire pressure to make sure it is adequate though.
Yes. You should be fine. A Honda CB650 should reach 63 mph at 9000 rpms. And, after all, on a motorcycle you should try and stay within the speed limit!